After the participant sit down and put on the VR glasses, the VR will detect how many degrees the head position has displaced from the neutral position (X= 0, Y = 0, Z = 0). The x, y and z describe the head alignment, and in the table (3.3), they explain the 3D axis (X, Y, Z). Also in fig 3.3 the participant's head is in X=5.027058 Y=2.466827 Z=2.93206, which explains the degree of deviation from the neutral position.

Cervical range of motion assessment is achieved through virtual reality. After detecting the static head posture, Participants will be asked to flex their necks as far as possible toward their chins and anterior chests. Then elevate the head to the neutral and extend the neck to the most tolerable range. Following that, he/she performs maximal neck side-bending in both directions along the coronal plane. Lastly, each participant is required to return the neck to an upright position for the examination of the maximum angle of neck rotation by "turning the chin toward the right and then left shoulders" without shrugging the shoulders. All of the tests will be repeated three times, and the averaged values of neck movement in each direction will be taken for analysis

The Neck Disability Index is a ten-item self-reported questionnaire describing daily life, pain, and concentration. Each item is rated on a score from 0-5, with 0 indicating no disability and 5 indicating extreme disability. To be clinically meaningful, there must be a minimum clinically important difference (MCID) of 5 points, at least, from a total of 50 (Table 3.2). Many studies have confirmed that the NDI has a high degree of validity and reliability. The NDI has also been used as an outcome measure in a number of studies involving the treatment of neck pain and patients with whiplash injury